1. Field of the Invention
The present invention relates to a color cathode ray tube, and more particularly, to a structure which can support a shadow mask spaced from an inside surface of a panel.
2. Background of the Related Art
In general, the cathode ray tube is used as an important component in a display, such as a TV receiver or computer monitor, for displaying a picture. A color of electron beams emitted from an electron gun in the cathode ray tube is selected at the shadow mask, for which the shadow mask is spaced for a required distance from the panel of the cathode ray tube by a supporting structure having a frame and the like.
FIG. 1 illustrates a section of an assembly of related art panel and a structure for supporting a shadow mask, referring to which the structure for supporting a shadow mask will be explained.
The structure for supporting a shadow mask is provided with a frame 3 having the shadow mask 2 fitted thereto under a tensile stress, supporting members 10 each fitted to an outer surface of the frame 3, and an elastic member 5 fixed to each of the supporting member. In more detail, the frame 3 has main frames 3a extended along long sides having the shadow mask 2 welded thereto directly, and subframes 3b extended along short sides connected to the main frames 3a for supporting the main frames 3a. In welding the shadow mask 2 to the frame 3, a compressive load is applied to the frame 3 in a short side direction for exerting a tension to the shadow mask 2 upon releasing the compressive load applied to the frame 3 after the welding is finished. The elastic member 5, a partially bent plate, having one side with a hole 5a inserted in a stud pin 1a on the inside surface of the panel 1 and the other side welded to the supporting member 10. To keep a position of the shadow mask 2 fixed regardless of varying conditions in the cathode ray tube, length, width, and angle of the bent of the elastic member 5 are taken into account before formation of the elastic member 5. The supporting member 10 has one side welded to the frame 3 and the other side welded to the elastic member 5 so as to be disposed between, and connect the elastic member 5 and the frame 3. There is a Self Thermal Compensating(STC) device 4 fitted to a bottom surface of the subframe 3b for preventing the tensile stress from being lost owing to a difference of thermal expansion coefficients between the frame 3 and the shadow mask 2 in a following process. Thus, the foregoing structure for supporting the shadow mask supports the shadow mask such that the shadow mask is maintained to be spaced a fixed distance from the panel 1. Particularly, the structure for supporting the shadow mask regulates position variation of the shadow mask 2 and the frame 3 caused by thermal expansion, to prevent color distortion.
In the meantime, a structure for supporting the shadow mask different from the foregoing structure may be used due to reasons on fabrication processes and design. One example of such structure is shown in FIG. 3.
Alike the structure in FIG. 1, the structure for supporting a shadow mask in FIG. 3 is provided with a frame 6, supporting members 10, and elastic members 5. The supporting members 10 and elastic members 5 are identical to the structure in FIG. 1. Only the frame 6 is different from the frame in FIG. 1. That is, the main frame 6a has a right-angled triangular section for reducing a residual deformation in the compressive deformation, and the subframe 6b connected between the main frames 6a has a low height for enhancing own rigidity.
Though the structure for supporting a shadow mask carries out basic functions of maintaining the shadow mask 2 spaced a distance from the panel 1 and regulating position variation of the shadow mask 2, the structure for supporting a shadow mask has the following problems.
First, welding between the supporting member 10 and the elastic member 5 is impossible due to the frame structure. The supporting member 10 is resistance spot welded to the frame 3, and 6, and the elastic member 5 is also resistance spot welded to the supporting member 10. In the resistance spot welding, welding objects are inserted between upper and lower electrodes, to weld the welding objects by means of a resistive heat of the welding objects, which is easy to weld and has a low equipment cost such that the resistance spot welding is used in most of process. In the case of the structure for supporting a shadow mask shown in FIGS. 1 and 2, a height of a position xe2x80x98Dxe2x80x99 of the hole 5a is adequate from the subframe 3b enough to weld the elastic member 5 to the supporting member 10 without interference of the welding electrodes. That is, since the height of position xe2x80x98Dxe2x80x99 of the welding spot for welding the elastic member 5 to the supporting member 10 is made adequate according to the position of the hole 5a, placing the welding electrodes to the welding objects is easy. However, in the structure for supporting a shadow mask shown in FIG. 3, since an overall height is designed low for enhancing a structural rigidity of the frame, the height of the position xe2x80x98Dxe2x80x99 of the hole 5a in the elastic member 5 is either inadequate or lower than the subframe 6b. That is, because the position xe2x80x98Dxe2x80x99 of a point for welding elastic member 5 to the supporting member 10 is formed lower then an upper surface of the subframe 6b, the welding electrodes can not be inserted. Consequently, though either change of a shape of the supporting member 10 or application of another method, is required, application of another method deteriorates a uniformity of quality, and requires a high investment cost.
Second, the work to fix the structure for supporting shadow mask at a fixed distance from a sidewall of the panel 1 is complicate. As described, since the frames 3 and 6 are compressed to give a tension to the shadow mask 2, there are residual deformations left in the main frames 3a and 6a and the subframes 3b and 6b. Eventually, dimensions of the frames 3 and 6 are changed after completion of welding of the shadow mask 2 to the frames 3 and 6 without fail. Alike the thermal expansion of the shadow mask 2, since the dimensional change of the frames 3 and 6 also affect color distortion of a picture, the dimensional change of the frames is required to be adjusted appropriately at the time of fitting the structure for supporting a shadow mask. However, change of a shape of the elastic member 5 is not easy because the elastic member 5 is form to be consistent with the gap preset between the supporting structure and the sidewall of the panel 1. Therefore, in order to maintain the gap between the structure for supporting a shadow mask and the sidewall of the panel 1, dimensions of deformed frames 3 and 6 are required to be measured every time, for adjusting deformation of the supporting member 10.
Accordingly, the present invention is directed to a structure for supporting a shadow mask that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a structure for supporting a shadow mask, in which resistance spot welding can be carried out regardless of a frame structure, facilitating to maintain a uniform welding quality.
Another object of the present invention is to provide a structure for supporting a shadow mask, which can maintain a gap between the panel and the sidewall with easy, for preventing color distortion.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the structure for supporting a shadow mask in a color cathode ray tube includes main frames each extended along a long side having the shadow mask welded thereto directly, subframes each extended along a short side connected to the main frames for supporting the main frame, plate type supporting members each fitted to a position of an outer surface of respective frames, and elastic members having one side coupled to a stud pin on an inside surface of the panel, and the other side fitted to the supporting member, wherein the supporting member of the subframe includes, a first and a second flanges opposite to each other extended downward vertically, and a parallel part extended horizontally between the first and second flanges.
The first flange preferably includes a horizontal bent part, and the parallel part has a length in a range of 4 mmxcx9c10 mm for inserting a low electrode.
Preferably, the bent part of the first flange is welded on a top surface of the frame for avoiding interference with a thermal compensating device in the shadow mask, and a length of a welding surface of the bent part of the first flange is adjusted for maintaining a distance between the supporting member and the stud pin constant.
Thus, the present invention permits application of resistance spot welding regardless of a frame structure, and to maintain a uniformity of welding quality and to prevent color distortion since maintenance of a gap to a panel sidewall is easy.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.